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//===- NameAnonGlobals.cpp - ThinLTO Support: Name Unnamed Globals --------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements naming anonymous globals to make sure they can be
// referred to by ThinLTO.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Utils/NameAnonGlobals.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/IR/Module.h"
#include "llvm/InitializePasses.h"
#include "llvm/Support/MD5.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"
using namespace llvm;
namespace {
// Compute a "unique" hash for the module based on the name of the public
// globals.
class ModuleHasher {
Module &TheModule;
std::string TheHash;
public:
ModuleHasher(Module &M) : TheModule(M) {}
/// Return the lazily computed hash.
std::string &get() {
if (!TheHash.empty())
// Cache hit :)
return TheHash;
MD5 Hasher;
for (auto &F : TheModule) {
if (F.isDeclaration() || F.hasLocalLinkage() || !F.hasName())
continue;
auto Name = F.getName();
Hasher.update(Name);
}
for (auto &GV : TheModule.globals()) {
if (GV.isDeclaration() || GV.hasLocalLinkage() || !GV.hasName())
continue;
auto Name = GV.getName();
Hasher.update(Name);
}
// Now return the result.
MD5::MD5Result Hash;
Hasher.final(Hash);
SmallString<32> Result;
MD5::stringifyResult(Hash, Result);
TheHash = std::string(Result.str());
return TheHash;
}
};
} // end anonymous namespace
// Rename all the anon globals in the module
bool llvm::nameUnamedGlobals(Module &M) {
bool Changed = false;
ModuleHasher ModuleHash(M);
int count = 0;
auto RenameIfNeed = [&](GlobalValue &GV) {
if (GV.hasName())
return;
GV.setName(Twine("anon.") + ModuleHash.get() + "." + Twine(count++));
Changed = true;
};
for (auto &GO : M.global_objects())
RenameIfNeed(GO);
for (auto &GA : M.aliases())
RenameIfNeed(GA);
return Changed;
}
namespace {
// Legacy pass that provides a name to every anon globals.
class NameAnonGlobalLegacyPass : public ModulePass {
public:
/// Pass identification, replacement for typeid
static char ID;
/// Specify pass name for debug output
StringRef getPassName() const override { return "Name Anon Globals"; }
explicit NameAnonGlobalLegacyPass() : ModulePass(ID) {}
bool runOnModule(Module &M) override { return nameUnamedGlobals(M); }
};
char NameAnonGlobalLegacyPass::ID = 0;
} // anonymous namespace
PreservedAnalyses NameAnonGlobalPass::run(Module &M,
ModuleAnalysisManager &AM) {
if (!nameUnamedGlobals(M))
return PreservedAnalyses::all();
return PreservedAnalyses::none();
}
INITIALIZE_PASS_BEGIN(NameAnonGlobalLegacyPass, "name-anon-globals",
"Provide a name to nameless globals", false, false)
INITIALIZE_PASS_END(NameAnonGlobalLegacyPass, "name-anon-globals",
"Provide a name to nameless globals", false, false)
namespace llvm {
ModulePass *createNameAnonGlobalPass() {
return new NameAnonGlobalLegacyPass();
}
}
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